With stereoscopic microscopes and surgical microscopes, there is a desire to reduce the distance between the position where one peers into the stereoscopic microscope and the observation object. In addition, it must be possible to attach a photographic device to the microscope and to also provide an observation station for a secondary observer, such as a surgical assistant, to observe an observation object. Further, the lateral extension of the microscope—the width of the microscope as viewed from the position of the primary observer—is preferred to be minimal for the primary observer in order to make it easier for the primary observer to utilize tools, such as tweezers, for working on an object within the field of view.
In addition, features are desired such as a high zooming ratio and having a variable-working-distance objective lens which enables the focus position to be changed without changing the position of the microscope. However, these features usually increase the distance between where the observer peers into the microscope and the observation object. Stereoscopic microscopes of the prior art that provide these features adopt an arrangement wherein two optical axes of a zooming optical system define a plane that is orthogonal to the optical axis of an objective lens by folding a portion of the light flux that exits the objective lens, as is done in the stereoscopic microscope disclosed in Japanese Laid-Open Patent Application No. 2001-208979, in order to lower the position where the observer peers into the microscope.
When attaching a photographic device and also when making observations by a secondary observer possible using an afocal relay system, the number of optical paths increases, thereby increasing the volume required for the optical paths and the volume required by the microscope. In Japanese Laid-Open Patent Application No. 2001-208979, a method for attaching and removing a unit to/from a microscope body is disclosed whereby only the unit that is necessary at the time of use is attached, thereby reducing the volume needed. However, as is shown in FIG. 8 of the present application, this requires that the attached unit be switched each time the microscope is adjusted for a right, a left, or an opposing position of the secondary observer in relation to the primary observer. Such an arrangement consumes time and thus is inefficient. While leaving multiple units attached does not require the switching of a single attached unit, such a practice adds an extra extension to the microscope, which is troublesome.